We demonstrate a highly efficient in-fiber out-coupling device. The core mode is coupled to the cladding by a tilted fiber Bragg grating and then the cladding mode is out-coupled from the optical fiber through V-grooved cladding. The light emitting characteristics are investigated experimentally and a maximum out-coupling efficiency of 54.8% is obtained.

A high-performance long-wave IR zoom sensor capable of 20× magnification using a 480×6 linear detector has been developed. The system magnification can be continuously adjusted by simply moving two lens groups, which also provides the means of athermalization of the images. The sensor image can be displayed in the 16 : 9-aspect-ratio high-definition TV format, which allows longer detection and recognition range than normal 4 : 3 TV format images without any loss of field of view. In order to correct the nonuniformity of the detector arrays, the two-point correction method has been applied using a thermoelectric cooler. Additionally, a new histogram processing technique suitable for characterization of the contrast distribution of thermal imagery has been proposed to enhance the image contrast and improve the detection capability.

This paper presents an algorithm to calculate polarized images, based on spatially adaptive wavelet analysis, in which image fusion theory is used. According to the principle and method of polarization imaging, the shortcomings of traditional methods in preserving detail information, removing the noise, and dealing with the misalignment of components in polarimetry are analyzed. Polarized-image calculation is a special case of image fusion, in which the combination rule is fixed. At the same time, wavelet-based image fusion method has a special advantage in acquiring rich detail information. To remove the effects of noise, we propose a spatially adaptive wavelet transform method. Then this method is extended to translation-invariant wavelets, which yield better results than the orthogonal wavelet transform when there is misalignment among components in polarimetry. Experiment and simulation results show that spatially adaptive wavelet-based polarization imaging yields significantly superior image quality to the traditional method.

The quickest method for generating a lightweight composite optic is to replicate an optical-quality glass tool onto a carbon-fiber-reinforced polymer (CFRP). However, fiber print-through creates an unacceptable sinusoidal surface roughness on replicated CFRP mirrors; chemical and thermal shrinkage during cure are commonly hypothesized to be the dominant causes. In order to mitigate fiber print-through, two methods of generating a polishable resin layer were investigated. The first method employs the application of a resin film to the CFRP surface. The second method, which is a more unconventional approach, generates a cocured resin layer using magnetic fibers. The latter approach is being developed to eliminate the application of additional resin layers to the CFRP surface, since additional layers present structural disadvantages.It was found that the magnetic fiber technique is comparable to the conventional approach in mitigating fiber print-through. Due to the presence of a 0.25-mm-thick buffer above the reinforcing phase, a final polishing step was used to attain optical quality features on all of the replicated specimens. CFRP and magnetic fiber samples were polished to within 50-Å rms roughness (1-µm to 1-mm bandwidth).

We describe a high-resolution, real-time 3-D shape measurement system based on a digital fringe projection and phase-shifting technique. It utilizes a single-chip digital light processing projector to project computer-generated fringe patterns onto the object, and a high-speed CCD camera synchronized with the projector to acquire the fringe images at a frame rate of 120 frames/s. A color CCD camera is also used to capture images for texture mapping. Based on a three-step phase-shifting technique, each frame of the 3-D shape is reconstructed using three consecutive fringe images. Therefore the 3-D data acquisition speed of the system is 40 frames/s. With this system, together with the fast three-step phase-shifting algorithm and parallel processing software we developed, high-resolution, real-time 3-D shape measurement is realized at a frame rate of up to 40 frames/s and a resolution of 532×500 points per frame.

We present a new algorithm for determining nano-scale feature dimensions of grating structures with a bright-field imaging tool. The algorithm is based on the intensity and focus quality of images obtained with varying amounts of defocus. Analysis of the intensity of optical images obtained at various focal positions demonstrates nanometer sensitivity with grating structures. An empirical quadratic model was developed to fit the experimental results of image intensity versus critical dimension.

A continuous-wave phase-shift laser range finder employs a novel multimodulation frequency method associating an undersampling analog-digital converter (ADC) with digital synchronous detection. This presentation greatly improves measured phase accuracy and reduces prior art scheme complexities. The novel patented design includes one phase-lock-loop (PLL) chip to produce a multimodulation frequency, one analog-to-digital converter operating at a low sampling rate, and an effective algorithm to calculate the final distance, which has encoded computing codes, and is implemented into compact computing circuits but without mixers and redundant components. The experimental results prove that a nonambiguity range is easily achieved to 1.5 Km when the modulation frequency is operated at 0.1 MHz. The measured accuracy approaches 2.9 mm using the same apparatus when the modulation frequency is tuned to 14.5 MHz. Dynamic range can reach 5.2×105 without a very high modulation frequency below 15 MHz, as revealed by a detailed analysis.

A quantitative bidirectional color schlieren system is presented, analyzed, and demonstrated. This method is capable of measuring simultaneously two components of deflection angles in two perpendicular spatial directions. The system acts as two independent schlieren setups with perpendicular knife-edge orientations. The method employs a two-color filter. A bidirectional heterodyne schlieren method is presented as well. The system is demonstrated by measuring various phase objects and compared with conventional schlieren. The sensitivity of the measurements can be significantly improved over the existing bidirectional schlieren methods. Moreover, the system is conceptually simple and inexpensive.

ZnO films have been deposited on SiO2/Si substrates by rf magnetron sputtering. The rms roughness of the sample's surface was surveyed by using an atomic force microscope, and is less than 10 nm. The theoretical reflectance of the air/film/middle layer/substrate structure has been deduced. In the light of this theoretical reflectance, the complex refractive index ñ()=n()+ik() of the sample below the interband absorption edge has been fitted with a Lorentz oscillator model. The absorption coefficient () of the sample is reported, and the result shows the sample has weak absorption around 490 nm.

This paper presents a study of the optical properties of amorphous hydrogenated silicon nitride (a-Si3N4:H) films under deposition temperature influence. The films were deposited by low-frequency plasma-enhanced chemical vapor deposition at temperatures of 200, 300, and 400°C and 0.6-Torr pressure. The mixture gases were silane (SiH4), ammonia (NH3), and hydrogen (H2). The optical properties of the films samples were obtained by means of the transmittance spectra and from spectroellipsometry measurements. Then, the optical parameters of the films were determined using the Swanepoel, Cauchy, and Sellmeier models. The refractive index dispersion curves were well fitted with both the Cauchy and the Sellmeier theoretical model. The equivalence between the parameters that characterize the two models is established.

The effect of Ge-composition on the transit-time limited frequency response of a vertical Si/Si1?yGey P-i-N photodetector has been investigated. The change in Ge-content (y) causes the changes in properties of the SiGe layer and the Si/SiGe interfaces and, hence, affects the transit time of carriers in the Si/SiGe photodetector. The results obtained from the analysis show that at low bias, the bandwidth of the photodetector initially increases with increase in Ge-content, but after an optimum value of Ge-content, the bandwidth starts decreasing. This optimum value increases with increase in applied bias.

A more useful model for calculating temperature distributions in kilowatt ytterbium-doped double-clad (YDDC) fiber lasers is proposed. Radiation, a major mode of heat transfer, is taken into account when the thermal conduction equations are solved for temperature distributions in the fiber tube. The results are compared with the ones obtained without considering radiative heat transfer. The presented model gives a qualitative explanation of the real operating conditions of YDDC fibers.

By using both GaAs and Cr4+:YAG saturable absorbers simultaneously in the same cavity, a xenon-flash-lamp-pumped doubly passively Q-switched intracavity-frequency-doubling Nd3+:YAG/KTP green laser is realized. This laser can generate a more symmetric shape and shorter pulse width compared to the solely passively Q-switched intracavity-frequency-doubling green laser with Cr4+:YAG or GaAs saturable absorber. A symmetric factor is defined to describe the temporal symmetry of the pulses quantitatively. The coupled rate equations under the plane-wave approximation are used to simulate the Q-switched process of the laser, and the numerical solutions agree well with the experimental results.

We describe the design and lasing characteristics of a miniaturized, chip-scale Nd:YAG slab laser. The Nd:YAG laser slab utilizes a retroreflecting corner to achieve a 17-cm optical path length with slab geometry of 10×12×2 mm. The laser is constructed, tested, and shown to successfully lase at 1064 nm under edge pumping with an AlGaAs diode laser at 808 nm. The slab laser is operated in a pulsed-pump excitation mode and shown to support a TEM10 single output mode. The fluence achievable from the edge pumping of this initial cavity geometry results in a 6.0% experimentally measured lasing efficiency.

A series-parallel model is introduced to calculate the effective thermal conductivities of hollow claddings of photonic crystal fibers (PCFs). The temperature distribution and thermal-optical properties of PCF lasers are studied by solving the heat transfer equations. The average power scaling of the PCF lasers in respect of the thermal effects is also discussed.

We present a detailed design of a simple, stable, and compact tapered amplifier (TA) diode system. Heat conductivity, strain release, and system alignment are taken into consideration for this design. Convenient access to the three-dimensional adjustments for collimation makes the system easy to align. The optical amplification is discussed as a function of injection of current and operating temperature for both a continuous-wave external cavity diode laser (CW-ECDL) and a mode-locked external cavity diode laser (ML-ECDL). With 5-mW CW-ECDL seeding power, 240 mW is achieved after the TA, 115 mW (48%) of which can be coupled into a single-mode fiber. With 0.75-mW average ML-ECDL seeding power, 80-mW average power, or about 11-W peak power (843-MHz repetition rate and 8-ps pulse width), is achieved after the TA, 39 mW (49%) of which can be coupled into a single-mode fiber. In both cases, the amplified light maintains the optical properties of the seeding light, showing the same mode suppression. The output power spatial mode quality is characterized with a camera and BeamView software. Output power stability is also discussed.

This study presents a numerical investigation into a novel approach for the inverse measurement of arbitrary strain distributions using a genetic algorithm (GA) and a fiber-Bragg-grating-based Sagnac interferometer. In the proposed method, a single uniform fiber Bragg grating (FBG) is bonded to the structure of interest such that it encounters the arbitrary strain field. The arbitrary strain distribution is then determined inversely from the transmission intensity spectrum using a GA population-based optimization process. The major advantage of the proposed approach is its use of a single, uniform FBG to sense arbitrary strain distributions. The approach provides a low-cost and computationally efficient means of detecting strain distributions in many smart-structure monitoring applications.

Based on the electro-optic (EO) polymer Mach–Zehnder interferometer (MZI) technology, IPITEK develops optical E-field sensor devices. As a receive antenna, the present device exhibits wide and flat bandwidth, up to 10 GHz. Testing the E-field sensor response was performed using a transverse electromagnetic (TEM) cell at frequencies from 0.2 to 1 GHz, and a set of 4 horn antennas at frequencies from 2.6 to 12 GHz. The minimum detectable E-field, Emin, was about 70 mV/(m) for an all-dielectric field sensor and was about 7 mV/(m) for a sensor with electrodes and a short wire loop antenna. A photonic down-conversion technique was developed to address bandwidth and receiving power limitations of the receiver photodetector. The down-conversion experimental results agree well with the theoretical heterodyne predictions. The EO polymer sensor sensitivity can be further improved by reducing the device optical insertion loss, optimizing the photodetector and detection circuitry, and using recently developed higher EO coefficients polymers.

We have developed a light-shielding technique for a star sensor that can shorten the baffle length. We achieved a baffle length of 120 mm, two-thirds that of a conventional two-stage baffle. The key idea is that the first lens of the imaging optics is designed as a near-hemispherical (NHS) lens that can work as an angle filter; high-incidence-angle rays are not permitted to be transmitted but low-incidence-angle rays from stars can be. A star sensor system with the new light-shielding technique onboard the SERVIS-1 satellite was launched in October 2003 as an experimental device. Though the in-orbit data verified its fundamental performance in capturing star images, undesirable solar background noise was observed in two corners of the field of view. Ray-trace simulations revealed that slight scattered light on the specular baffle surface entered the NHS lens and reached the corners of the image sensor through a multireflection path inside the lens. We redesigned the baffle and confirmed that stray light was reduced below maximum acceptable levels in a ground test. The star sensor with redesigned baffles is planned to be installed as the main attitude sensor for the SERVIS-2 satellite to be launched in 2008 or later.

The spectrum bandwidth of long-period fiber grating (LPG) for various high-order cladding modes are analyzed in detail by two-mode coupled-mode equations and applied to design narrow bandwidth optical add-drop multiplexer (OADM) based on two parallel LPGs. In addition, in order to obtain the maximal power transmission, we further derive the structure parameters of OADM such as the distance between two parallel fibers and the length of two long-period fiber gratings according to four-mode coupled-mode equations. As far as this OADM structure is concerned, it is obvious that LPG will dominate the entire bandwidth if LPG has enough narrow bandwidth in comparison with the 2×2 coupler. In other words, we can easily use LPG to estimate the bandwidth of OADM before starting to design it. In order to survey the feasibility of the above statement, the spectrum bandwidths of LPG and OADM for the various bandwidth of high-order cladding modes are compared and analyzed. Utilizing the four steps proposed in this paper, the numerical results have demonstrated that we can use the high order cladding mode =125 to design the OADM that possesses narrow FWHM (<0.4 nm) and meets the DWDM system

The paper, the method of three-dimensional refractive index measurement in optical fibers. The emphasis is put on experimental technique and instrumentation; however, important theoretical topics are briefly described (e.g., diffraction influence on measurement results). The experimental setup and measurement algorithm are presented in detail. Experimental results include measurement of the following objects: multimode optical fiber; optical fiber splice; and single-mode optical fiber. Sources of errors and accuracy of the method are analyzed. As a conclusion, we discuss the limitations and possible other applications of tomographic microinterferometry.

Two fast and accurate algorithms based on the orthogonal polynomial approximation and the Chebyshev polynomial interpolation for obtaining the actual field solutions of a fiber with arbitrary refractive index profile are presented. These solutions in turn can be used to evaluate the dispersion parameters of the fiber. The numerical methods are compared in terms of their performances, viz., complexity and accuracy. The method based on the orthogonal polynomial approximation (OPA) is simple in principle and easy to implement on a computer, and it has several advantages compared to the method based on the Chebyshev polynomial interpolation (CPI).

Group velocity dispersion (GVD) and effective mode area (Aeff) of solid core honeycomb cladding photonic crystal fiber (HPCF) with different doping levels are investigated theoretically. Both total internal reflection and photonic bandgap guiding mechanisms are shown to be available in this fiber structure with the changes of doping levels. GVD is shown to be dominated by the large waveguide dispersion corresponding to the fiber structure. Numerical results show that HPCF can achieve small Aeff with low air-filling fraction. One special case is given to demonstrate the potential of HPCF in dispersion compensation.

The preconfiguration cycle (p-cycle) is an excellent protection scheme that benefits both the fast recovery time and the efficient resource utilization in wavelength-division-multiplexing (WDM) mesh networks. Before providing protection for any link whose end nodes are both on the p-cycle, the spare capacity assignment for the p-cycles is a very important step for p-cycle design in WDM networks. We present a heuristic scheme, called the p-Cycle Capacity Assignment Algorithm (CCAA), to achieve an optimal capacity assignment of p-cycles in WDM networks without using Integer Linear Programming (ILP). CCAA can configure the p-cycles with good actual efficiency because it first consumes the spare capacity of the links where more spare capacity exists. This scheme is more suitable for the design of maximum p-cycle restorability with a given spare capacity distribution. When allocating the spare capacity for the p-cycles in WDM mesh networks, this scheme considers the actual distribution of the working capacity and the spare capacity of a certain traffic pattern. The performance of CCAA is evaluated by computer simulations on the real-world network topology.

Atmospheric optical wireless communication is a fading channel because of the effect of atmospheric attenuation. We introduce a novel turbo code named the two-fold turbo code scheme to provide high performance for optical wireless communication. To use the two-fold turbo code over optical wireless channels, first deduce the formula of atmospheric channel signal-noise-ratio versus atmospheric visibility, then analyze the coding and decoding principle of the two-fold turbo code. Simulations show that the proposed two-fold turbo code significantly improves the performance of the system compared to the common turbo code.

In preparation for the Laser Interferometer Space Antenna (LISA) space mission, the prototype engineering model of the LISA-Pathfinder optical bench instrument has been built and tested. The instrument is the central part of an interferometer whose purpose is to measure the separation of two free-floating test masses in the spacecraft, with required accuracy to a noise level of 10 pm/Hz?1/2 between 3 mHz and 30 mHz. This will allow the spacecraft to achieve drag-free flight control to a similar level, as a demonstration of technology capability for detection of gravitational waves in the later LISA mission. The optical bench design, fabrication, and experimental results are described in detail, with attention to the strategies for building and alignment. These are particularly problematic in this instrument due to restrictions on the allowable materials and devices, the limited size, the tight alignment requirements for interferometry and interfaces, and the challenging environment specification for space flight. The finished optical bench was integrated to the complete optical metrology package for system-level tests, which were successful, both in meeting the metrology accuracy and in environmental testing. This verifies the feasibility of the design and build methods demonstrated here for use in the space-flight version.

A phase-shifting method and a Savart shearing interferometer using it are introduced. Experimental results conducted to verify the method and interferometer are presented. The results confirm the validity of the method and the validity and applicability of the interferometer.

Propose here unique wavelength and hybrid wavelength-polarization and wavelength-polarization-time-multiplexed heterodyne optical interferometers using an internal self-referencing scheme enabling Angstrom level sensitivity optical path-length measurements. As a first step, a proof-of-concept wavelength multiplexed scanning heterodyne interferometer is built to test the surface quality of a test mirror, demonstrating ±100 Å profile variations with a 0.9 Å accuracy. The hybrid wavelength-polarization and wavelength-polarization-time-multiplexed interferometers can be used to form spectrally coded distributed sensors.

A simple, inexpensive, and efficient stabilized holographic recording setup is described which precludes the destructive fringe movement encountered in long-lasting holographic exposures. Utilizing a straightforward methodology, stability greater than /25 (recording wavelength =532 nm) for holographic recording sessions longer than 6 h can be achieved. Due to the software basis of this design, in the LabVIEW platform, the functionality of expensive hardware components is provided in software. Moreover, this setup is modularly designed and can be easily replicated for multiple labs, with the need only of the following hardware components: a piezo-shifting mirror, a computer, a data-acquisition card, and a photodetector.

Calculations of the spectral cloud reflectance over bare soil and vegetation are performed in the framework of the asymptotic radiative transfer theory. A simple equation for the threshold value (THV) of the albedo of the underlying surface is derived. The cases of underlying surfaces with the albedos smaller than the THV can be treated as if the albedo of the surface is equal to zero in satellite cloud remote sensing problems.. It was found that the THV increases with the cloud optical thickness. Also, the differences in light transmission by clouds over bare soil and vegetation are studied.

This research addresses the problem of tracking a moving point target in a time sequence of hyperspectral images; we focus on the detection of moving targets with staring technologies. In these applications, the images consist of targets moving at subpixel velocity in backgrounds that are influenced by both evolving clutter and noise. The demand for a low false-alarm rate on one hand and a high probability of detection on the other makes the tracking a challenging task. The use of hyperspectral images should be superior to current technologies, due to the benefit of simultaneously exploiting two target-specific properties: the spectral target characteristics and the time-dependent target behavior. We propose an algorithm that is in two steps. The first step is the transformation of each of the hyperspectral images forming the sequence into a two-dimensional image using a known point-target detection-acquisition algorithm. In the second step, target detection and tracking are performed by the means of time-domain processing. A match-filter technique is used for the hyperspectral image transformation; a variance-filter algorithm is developed to detect the presence of targets from the temporal profile of each pixel while suppressing clutter-specific influences.

Template-matching techniques for automatic detection of multiple, extended, and low contrast targets in infrared maritime scenarios are described and analyzed. In particular, we focus our attention on the specific area of the sea around the horizon, where common techniques of clutter removal, based on target contrast only, fail. Targets of interest are ships along the horizon line in adverse atmosphere conditions, with dim contrast with respect to the background. A database of ship images is used for the analysis. We conclude that the normalized cross-correlation (NCC) technique is a reasonable choice for this application due to its capability to provide an estimate of the similarity between images, even if they present different energy levels and are corrupted by noise. It also is more tolerant to the geometric distortions. After a description of the test setup, simulation results are presented to show the performances of the proposed technique; examples using both synthetic and real images are considered.

Watermarking schemes for authentication purposes are characterized by three factors: security, resolution of tamper localization, and embedding distortion. Since the requirements of high security, high localization resolution, and low distortion cannot be fulfilled simultaneously, the relative importance of a particular factor is application-dependent. Moreover, blockwise dependence is recognized as a key requirement for fragile watermarking schemes to thwart the Holliman-Memon counterfeiting attack. However, it has also been observed that deterministic dependence is still susceptible to transplantation attack or even simple cover-up attack. This work proposes a fragile watermarking scheme for image authentication, which exploits nondeterministic dependence and provides the users with freedom of making trade-offs among the three factors according to the needs of their applications.

A wavelet-based robust image coding technique for image transmission over noisy channels is presented here. The system combines classification and optimal bit allocation along with robust quantization to produce an inherent error-resistant bitstream without channel coding. In order to improve coding efficiency, an iterative algorithm is developed for implementing optimal bit allocation involving both rate distortion and channel optimization. Also, a modified channel optimized uniform trellis coded quantization (TCQ) with a low computational complexity, yet an effective performance, is proposed and used to provide robust quantization. The system achieves both efficient image compression and robust image transmission over noisy channels. Computer simulations indicate that the proposed scheme is effective, even under mismatched channel conditions, and the performance is competitive with other robust image compression techniques.

The objective of this work is to give an approximate statistical model of the distribution of 4×4 pixel natural image patches B. Given the huge size of the sample space, we collect the required statistics not directly over B, but, instead, over a fractal compression inspired representation of B, namely by a triplet (DB,µB,B), with B being the patch's contrast, µB its brightness, and DB a codebook representation of the mean-variance normalization of B:(B?µB)/B. While not coinciding exactly with the true natural patch density p(B), the density (B)=p(DB,µB,B) should give an adequate approximation of p(B), because BBDB+µB. Our first main result is a factorization of the probability density p(D,µ,) as p(D,µ,)p(D)p(µ)p()(||B||), with being a high-contrast correction. Here, the brightness term p(µ) is largely irrelevant, and our second main result deals with the structure of the other two factors, showing that p() follows an exponential distribution, and that p(D) is uniformly distributed with respect to volume in image space. These results are largely independent of the codebook used.

To reduce ringing and preserve edges, smoothness must be adaptive in image restoration. We improve on the Laplacian operator and propose an anisotropic regularizing operator. The variables are substitutes for the constants in the Laplacian operator. The anisotropic regularizing operator can control adaptively the direction and amount of smoothing in image restoration. Although the anisotropism idea is closely related to edge-preserving regularization, the anisotropic regularizing operator has different regularization terms and simpler conditions. The iterative equations of anisotropic regularizing operators have unified form. By imposing some constraints, iterative equations can become equations of image restoration with ringing reduction and edge-preserving regularization. The method for linearizing the anisotropic regularization term is provided.

Finding the distance of an object in a scene from intensity images is an essential problem in many applications. In this work, we present a novel method for depth recovery from a single motion and defocus blurred image. Under the assumption of uniform lateral motion of the camera during finite exposure time, both the pinhole model and the camera with a finite aperture are considered. It is shown that the image blur produced by uniform linear motion of the camera is inversely proportional to the distance of the object. Furthermore, if the speed of the relative motion is known, the depth of the object can be acquired by identifying the blur parameters. An image blur model is formulated based on geometric optics. The blur extent is estimated by intensity profile analysis and focus measurement of the deblurred images. The proposed method is verified experimentally using different types of test patterns in an indoor environment.

Bit allocation analysis is concerned with the study of efficient combinations of quantizer-based allocations and bit consumption by a model capable of numerical application. The modus operandi of bit-allocation analysis is the use of set theory and the fundamental theorems of mathematical optimization. The most important concept in this analysis is the efficient allocation process, which represents a combination of quantizer-based allocations and bit consumption such that no bit allocation of a quantizer can be increased without decreasing another quantizer's allocation or increasing consumption. The main result of this paper allows one to characterize the concept of efficient allocation process by profit maximization with respect to any allocation-consumption combination among competing quantizers. In bit allocation analysis, the system makes a choice from the set of efficient allocations at any given time by using the appropriate strategy for computing the profit vector. It may allow attending to different parameters of interest at different bit rates within the same spatial locations. It is a typical linear programming problem, for which computational methods are well known and widely used in practice. The comparative performance of the 3-D set partitioning in hierarchical trees with motion-compensated temporal filtering and the proposed coder (without motion filtering) using bit allocation analysis is here evaluated on a set of sequences of moving targets.

A 64×32 liquid-crystal-on-silicon (LCOS) backplane with a novel framebuffer pixel array has been designed and fabricated using the AMI Semiconductor 0.5-µm double-poly triple-metal CMOS process. The pixel circuit described herein increases the brightness significantly without sacrificing image contrast ratio. Characteristics of various liquid-crystal modes applicable to field sequential color displays have been investigated. The LCOS microdisplay, employing an optimized optically compensated birefringence mode, demonstrates fast response times (OFF=0.3 ms, ON=1.2 ms) enabling a frame rate of 720 Hz, with a potentially high contrast ratio of up to 1600:1.

We introduce the novel parallel-aligned liquid crystal wavefront corrector (LC WFC) with 1920×480 pixels designed to operate at phase-only mode. The optical characteristics of the LC WFC were measured. The theory of diffractive optics is used to correct the aberrated wavefront. The measured peak-valve (PV) value of the wavefront is 9.956 before correction and 0.837 after that. Moreover, the measured root mean square (rms) value of the wavefront is 2.202 before correction and 0.124 after that. It expands LC devices' application fields.

The performance of acousto-optic correlators (AOC) in spread-spectrum receivers is considered. The received pseudorandom sequences are correlated with reference ones in an acousto-optic cell. In particular, the effects of receiver filtering on the AOC processing gain are analyzed in the presence of additive white Gaussian noise (AWGN). The signal processing method is presented. For ideal AOCs, simple analytical expressions are derived for two different types of receiver filters: ideal and RC first-order filters. The results are given in terms of the ratio of the code rate to the filter bandwidth. They show approximate processing gain losses of 4 dB for the first type and 1 dB for the second type for =5. For real AOCs, the results are obtained from numerical simulation.

A complete analytical model of the polarization characteristics of a semiconductor laser amplifier in a loop mirror (SLALOM) is presented. Based on this model, various kinds of output for all-optical conversion of non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) signals, based on a simple SLALOM scheme, are analyzed theoretically. Simulation results were in good agreement with experimental results on 20-Gbit/s all-optical NRZ-to-PRZ conversion. The results show that the theoretical model proposed in this paper is right, and proper polarization-state control is helpful for improving the output characteristics in all-optical pattern conversion.

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Journal of Applied Remote SensingJournal of Astronomical Telescopes Instruments and SystemsJournal of Biomedical OpticsJournal of Electronic ImagingJournal of Medical ImagingJournal of Micro/Nanolithography, MEMS, and MOEMSJournal of NanophotonicsJournal of Photonics for EnergyNeurophotonicsOptical EngineeringSPIE Reviews